POTENTIAL OF AN ORGANOSILICONE SURFACTANT TO IMPROVE SOIL WETTABILITY AND AMELIORATE FAIRY RING SYMPTOMS CAUSED BY MARASMIUS-OREADES

Currently, chemical control of fairy ring caused by Marasmius oreades is not feasible, in part because colonized soil is very repellent to pesticidal solutions. Fungicidal control, however, might be successful if a surfactant was used to increase soil wettability. Of 13 surfactants screened for ability to enhance solution uptake by infested soil cores, the organosilicone, Silwet L-77, was most effective, followed by Citowett Plus and Agsurf. In a second, similar experiment, Silwet L-77 was more effective than the other two surfactants in increasing water uptake by both infested and uninfested soil cores. Silwet L-77 concentrations of 0.98-3% were equally effective in increasing grass production, relative to the water control, on colonized and uncolonized turf, under greenhouse conditions. At concentrations of 2 % or higher, but not at concentrations of 0.016% to 1.0%, Silwet L-77, Citowett Plus, and Agsurf prevented M. oreades growth in liquid culture. Silwet L-77, and perhaps other organosilicone surfactants, seemingly have considerable potential for the management of fairy ring by improving uptake of water, or as carriers of biological or chemical control agents.